This invention relates to a superconductor, and more particularly to a compound thin film superconductor.
Recently, it was proposed that the materials of a Y-Ba-Cu-O system are higher temperature superconductors [M. K. Wu et al, Physical Review Letters Vol. 58, No. 9, 908-910 (1987)].
More recently, materials of a Bi--Sr--Ca--Cu--O system were found to be electrically superconducting above 100.degree. K., and materials of a Tl--Ba--Ca--Cu--O system exhibiting zero electrical resistance at still higher temperature were successively found.
The details of the superconductivity mechanism of these high Tc superconducting oxides are not clear, but there are possibilities that the transition temperature of these materials may become higher than the room temperature. Superior performances to the conventional binary compounds as the electrical superconductor are expected.
These high Tc superconducting oxides, however, can only be made, at the current technology, through the step of sintering. Therefore, these materials are only available in the forms of ceramic powders or ceramic blocks.
For bringing materials of this kind into practical use, it is strongly desired that the materials are shaped in thin films or in wires. At the current technology, tested specimens are poor in reproducibility and reliability. It is generally considered that good superconducting films and/or wires of these materials are very hardly supplied. Further, the films of these materials are formed on single crystal substrates and the cost of the substrate is expensive.